How to make multi Slect requried

Hi there,

I am using Custom UI with atlaskit.
I am trying to make multi select required.

My code:

<Form onSubmit={onSubmit}>
                {({formProps}) => (
                    <form {...formProps}>
                        { any, index: number) => {
                            console.log(mapping, index);
                            return (<div>
                                    <h4>Mapping Configuration {index + 1}</h4>
                                        <Field<Value<Option, true>>
                                            name={configurationType.toLowerCase() + `Assets[${index}]`}
                                            label={"Select a " + configurationType + " assets"}
                                            {({ fieldProps: { id, }, error }) => (
                                                    <Select inputId={id} {} options={assetOptions} isMulti />
                                                    {error && <ErrorMessage>{error}</ErrorMessage>}
                            <Button type="submit" appearance="primary">
                                Save Customization

I used isRequired but I am still able to submit this form even thought select is empty. How to make this select required?
Thank you